Sunday, May 18, 2014

Precipitation Deficits

As we move into the heart of the fire season, it seems like a good time to highlight how little precipitation has fallen recently. If someone said that both Barrow and Ketchikan recorded above normal precipitation for the last two months, it would be reasonable to assume than many places in between were also above normal. That is most definitely not the case. Over the two month time period between March 17th and May 16th, I totaled all stations that recorded precipitation and have published NCDC normal precipitation values. The total measured precipitation during that time period was then compared to the normal precipitation to come up with a percentage of normal.

Values were only counted for days where a precipitation value was entered (including 0.00"). Both the numerator and denominator in the calculation only use days with valid data; i.e., if no precipitation value is entered on a day, the normal value for that date is excluded as well. A station must have 56 or more days of usable data during this time period for inclusion in the analysis. In many cases, missing data is a result of the lag time until data entry – not truly missing data. Figure 1 shows all 67 stations that met the inclusion criteria in Alaska. Figure 2 shows the same information but is zoomed in on the Fairbanks area. Figure 3 shows all of the data used to make the first two figures.

Figure 1. Percentage of normal precipitation in Alaska for for the 61-day period between March 17th and May 16th, 2014. Only stations with 56 or more days of usable data were included.

Figure 2. Percentage of normal precipitation around Fairbanks for the 61-day period between March 17th and May 16th, 2014. Only stations with 56 or more days of usable data were included. Note: the same legend items are used for Figures 1 & 2. Therefore, Figure 2 has several unused categories.

Figure 3. Table of data used to generate Figures 1 & 2. Only stations with 56 or more days of usable data were included.

1 comment:

Here in Fairbanks it appears that leaf development on the valley floor is slow, and my white spruce are dropping dead needles like never before. The roof and yard are covered with a layer of those needles.

Is this a return to the early arid Preboreal Holocene era? No, but it's fun to wonder why it's been dry this year.